Automated cleaning of wafer plating assembly

ABSTRACT

Disclosed herein are cleaning discs for cleaning one or more elements of a semiconductor processing apparatus. In some embodiments, the disc may have a substantially circular upper surface, a substantially circular lower surface, a substantially circular edge joining the upper and lower surfaces, and a plurality of pores opening at the edge and having an interior extending into the interior of the disc. In some embodiments, the pores are dimensioned such that a cleaning agent may be retained in the interior of the pores by an adhesive force between the cleaning agent and the interior surface of the pores. Also disclosed herein are cleaning methods involving loading a cleaning agent into a plurality of pores of a cleaning disc, positioning the cleaning disc within a semiconductor processing apparatus, and releasing cleaning agent from the plurality of pores such that elements of the apparatus are contacted by the released cleaning agent.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority to U.S. patentapplication Ser. No. 13/563,619, filed Jul. 31, 2012, titled “AUTOMATEDCLEANING OF WAFER PLATING ASSEMBLY,” which claims the benefit of U.S.Provisional Patent Application No. 61/513,993, filed Aug. 1, 2011,titled “AUTOMATED CLEANING OF WAFER PLATING ASSEMBLY,” all of which areincorporated herein by reference in their entireties for all purposes.

TECHNICAL FIELD

The present disclosure relates to apparatuses and methods for cleaning asemiconductor holding and processing apparatus and, in particular, forremoving unwanted metal deposits from a wafer handling and processingapparatus and, even more particularly, from a plating assembly.

BACKGROUND

Electrochemical deposition may be employed at various points in theintegrated circuit (IC) fabrication and packaging processes. At the ICchip level, damascene features are created by electrodepositing/platingcopper within vias and trenches to form multiple interconnectedmetallization layers. Above the multiple metallization layers, the“packaging” of the chip begins. Various wafer level packaging (“WLP”)structures may be employed, some of which contain alloys or othercombinations of two or more metals or other components. For example, thepackaging may include one or more “bumps” made from solder or relatedmaterials. A typical example of a plated bump starts with a conductivesubstrate seed layer (e.g. a copper seed layer) having an “under bump”diffusion layer of plated nickel (e.g. 1-2 μm thick and about 100 μmwide) under a film of lead tin solder plated pillar (e.g. 50-100 μmthick and about 100 μm wide). After plating, photoresist stripping, andetching of the conductive substrate copper seed layer, the pillar ofsolder is carefully melted or “reflowed” to create a solder “bump” orball attached to the under bump metal.

As an alternative to this scheme (often referred to as “copper pillar”or “micro pillar”), an under bump of a non-solder plated “pillar” metalsuch as copper, nickel, or a combination of these two, is created belowa typically much thinner and smaller solder film than above. In thisscheme, useful in achieving tight/precise feature pitch and separationcontrol, the copper pillars may be for example 50 μm or less in width,features separated from one another by 75-100 μm center to center, andthe copper may be 20-40 μm in height. On top of the copper pillar, anickel barrier film, e.g., about 1-2 μm thick, is sometime used toseparate the copper from the tin containing solder and thereby avoid asolid state reaction to form various mechanically and chemicalundesirable bronzes. Finally, a solder layer, typically 20-40 μm inthickness is added. This scheme also enables a reduced amount of solderfor the same features size, reducing cost or total amount of lead (inlead containing solders) in the chip.

Lead-tin materials provide good quality “bumps” for packaging and arevery easy to plate. Unfortunately, environmental and health-safetyconcerns regarding lead's toxicity is driving a movement away from theuse of lead containing solders. For example, the RoHS initiative(Directive 2002/95/EC of The European Parliament) requires entities tochange from the established tin-lead process to a lead free one. Logicalreplacement bump materials include indium, tin, tin-silver binarymaterials, tin-bismuth binary materials, and tin-silver-copper ternarymaterials. Materials based upon tin alone can suffer from a number offundamental limitations and application difficulties, such as thetendency to form large single grained balls with varying crystalorientations and thermal expansion coefficients, and “tin whiskers”which can lead to interconnect-to-interconnect shorting. The binary andtertiary materials may perform better and alleviate some of these puretin issues, potentially, at least in part, by precipitating a largenumber of small grain inclusions of the non-tin component as part of thesolder melt to solid state freezing process. Certain compositions madefrom silver-tin alloys, may demonstrate these characteristics. Thus,silver-tin solder alloy bumps are of particular interest.

SUMMARY OF THE INVENTION

Disclosed herein are cleaning discs for cleaning one or more elements ofa semiconductor holding and processing apparatus. In some embodiments,the disc may have a substantially circular upper surface, asubstantially circular lower surface, a substantially circular edgejoining the upper and lower surfaces, and a plurality of pores openingat the edge and having an interior extending into the interior of thedisc. In some embodiments, the pores are dimensioned such that acleaning agent may be retained in the interior of the pores by anadhesive force between the cleaning agent and the interior surface ofthe pores. In certain such embodiments, the edge may have an upperportion joined to the upper surface of the disc as well as a lowerportion joined to the lower surface of the disc which has a radius lessthan the radius of the upper portion. The openings of the plurality ofpores may be located in this lower portion of the edge, and in someembodiments, the mean height of the lower portion of the cleaning disc'sedge may be about or between 0.5 mm and 3.0 mm. In some embodiments, thediameter of the disc is about or between 150 mm and 500 mm. In someembodiments, the cleaning disc may be constructed at least partiallyfrom a corrosion resistant metal such as stainless steel, titanium, ortantalum. In some embodiments, the cleaning disc may be constructed atleast partially from a corrosion resistant thermoplastic polymer such asa polycarbonate, or polyphenylene sulfide or polyvinylidene fluoride.

In some embodiments, the plurality of pores may have substantiallycircular openings, and in certain such embodiments, the pores may bedrilled holes. In some embodiments, the substantially circular openingsmay have diameters about or between 0.25 mm and 1.25 mm. In someembodiments, an interior surface of the pores may be hydrophilic.

In some embodiments, the cleaning disc may include a cleaning agentadsorbent element which, in some embodiments, is composed at leastpartially of a fibrous, and/or cloth-like, and/or filter material forretaining the cleaning agent. The adsorbent element may be configured tosupply cleaning agent to the plurality of pores.

Also disclosed herein are methods of cleaning one or more elements of asemiconductor holding and processing apparatus. In some embodiments, themethods include loading a cleaning agent into a cleaning disc byreceiving the cleaning agent into a plurality of pores within one ormore edges of the cleaning disc, holding the cleaning agent inside theplurality of pores, positioning the cleaning disc within the processingapparatus such that the plurality of pores are adjacent to the one ormore elements of the apparatus to be cleaned (the one or more elementsto be cleaned normally being adjacent to a semiconductor wafer when awafer is held in the processing apparatus for processing), and releasingcleaning agent from the plurality of pores such that the one or moreelements of the apparatus to be cleaned are contacted by the releasedcleaning agent. In some embodiments, the method of cleaning may be usedto clean a semiconductor holding and processing apparatus after theapparatus has been used to electroplate a semiconductor wafer.

In certain embodiments, the cleaning methods disclosed herein mayfurther include removing cleaning agent from one or more outsidesurfaces of the cleaning disc, after the loading step just described,but prior to the positioning step just described. In certain suchembodiments, such removal of cleaning agent may include spinning thedisc at a rotation rate such that cleaning agent flows off the outsidesurfaces of the disc, but cleaning agent substantially remains withinthe plurality of pores, such as, for example, at a rotation rate aboutor between 50 RPM and 250 RPM. In certain such embodiment methods, theviscosity of the rinsing agent may be less than the viscosity of thecleaning agent.

In certain cleaning methods disclosed herein, loading the cleaning agentin the cleaning disc may include immersing a portion of the cleaningdisc in the cleaning agent, and may further include drawing the cleaningagent into the pores by capillary action. In certain cleaning methodsdisclosed herein, holding the cleaning agent may further includeadhering the cleaning agent to the interior surfaces of the plurality ofpores.

In certain cleaning methods disclosed herein, releasing cleaning agentfrom the cleaning disc's plurality of pores may include spinning thedisc at a rotation rate such that the one or more elements of thesemiconductor holding and processing apparatus to be cleaned arecontacted by the released cleaning agent, but the released cleaningagent does not substantially flow continuously out of the plurality ofpores. In certain embodiments, a cleaning method may further includesucking cleaning agent back into the cleaning disc's plurality of pores,after the cleaning agent was released to contact the one or moreelements of the semiconductor holding and processing apparatus to becleaned. In certain such embodiments, suction is created by reducing therotation rate of the disc relative to the rotation rate used forreleasing cleaning agent. The cleaning methods disclosed herein mayfurther include removing the cleaning disc from the processingapparatus, and unloading cleaning agent from the plurality of pores byspinning the disc. In some embodiment methods, the disc may be spun at arotation rate of about or greater than 500 rpm to unload cleaning agentform the plurality of pores.

Cleaning methods disclosed herein may be used to clean various elementsof a semiconductor holding and processing apparatus. In someembodiments, the one or more elements of the processing apparatus to becleaned include the lip seal of the processing apparatus, and/or the cupbottom of the processing apparatus. In some embodiments, the cleaningmethod removes metal deposits from one or more elements of thesemiconductor holding and processing apparatus. In certain suchembodiments, the metal deposits may include an alloy of tin and/or analloy of indium.

Cleaning methods disclosed herein may employ a variety of cleaningagents. In some embodiments, a cleaning method may include an acid as acleaning agent. In certain such embodiments, the acid may be nitricacid, and it may have a concentration in the cleaning agent of about 10%or more by weight. In some embodiments, the cleaning agent may include ametal complexing agent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a substrate handling and processingapparatus.

FIG. 1B is a cross-sectional view of a cup/cone clamshell assemblyholding a semiconductor wafer.

FIG. 2A is a perspective view of one embodiment of a cleaning discviewed from below.

FIG. 2B is a cross-sectional perspective view of a cleaning disc held ina cup/cone clamshell assembly.

FIG. 2C is another cross-sectional perspective view of a cleaning discheld in a cup/cone clamshell assembly.

FIG. 3 is a schematic drawing of one suitable automated substrateplating tool apparatus.

FIG. 4 is a flow chart that outlines a variety of embodiment methodsdisclosed herein.

DETAILED DESCRIPTION

Deposition of silver-tin alloys is accomplished by a challenging processthat frequently employs an inert anode (rather than the potentially moredesirable “active” or soluble anode). Part of the difficulty in using anactive anode for this and similar systems results from the very widelyseparated electrochemical deposition potentials of silver and tin; thestandard electrochemical potentials (E₀s) of the metals are separated bymore than 0.9 volts (Ag⁺/Ag: 0.8V NHE, Sn⁺²/Sn: −0.15V). Since elementalsilver is substantially more noble and inert than elemental tin, it willtherefore undergo a displacement reaction and electroplate out ofsolution onto the surface of a tin anode or tin/silver anode. Thischemical “short circuit” removes (strips or extracts) the relatively lowconcentration of silver from the plating solution continuously,resulting in both an uncontrollable process as well as the formation ofreduced silver metal on the tin anode.

Methods and apparatuses for efficient and high-quality plating whenusing potential-differing set of metals are described in U.S. PatentApplication No. 61/502,590, filed Jun. 29, 2011, entitled“ELECTRODEPOSITION WITH ISOLATED CATHODE AND REGENERATED ELECTROLYTE,”naming Steven T. Mayer as inventor; U.S. Patent Application No.61/418,781, filed Dec. 1, 2010, entitled, “ELECTROPLATING APPARATUS ANDPROCESS FOR WAFER LEVEL PACKAGING,” naming Steven T. Mayer, et al. asinventors; and U.S. patent application Ser. No. 13/172,642, filed Jun.29, 2011, entitled, “CONTROL OF ELECTROLYTE HYDRODYNAMICS FOR EFFICIENTMASS TRANSFER DURING ELECTROPLATING,” naming Steven T. Mayer et al, asinventors; each of which is hereby incorporated by reference in theirentirety herein for all purposes. Despite the existence of relativelygood quality plating regimes for plating two or more metals, when thereis a large difference in the plating potentials of the metals unwantedmetal oftentimes plates out on surfaces of the wafer holder and/orhandler. Thus there remains the question of how to deal with theseunwanted metal deposits. Although the discussion herein is frequentlycouched in terms of silver tin plating, the principles discussed applyequally well to any unwanted deposits. That is, the methods andapparatuses disclosed herein may be used for dealing generally withunwanted metal or even non-metal deposits.

Accordingly, described herein are methods and apparatuses for cleaningwafer handling and processing equipment, and in particular handing andprocessing equipment that holds and rotates a semiconductor wafer duringprocessing. The processing may involve plating or any othersemiconductor fabrication process which leaves unwanted materialdeposited on the wafer handling and processing equipment. In someembodiments, the unwanted material to be removed from various elementsof the apparatus are metal deposits. In certain such embodiments, themetal deposits include an alloy of tin, or more particularly an alloy oftin and silver, or still more particularly an alloy of tin, silver, andcopper. In some embodiments, the metal deposits may include an alloy oftin and bismuth, or an alloy of indium, or more particularly an alloy oftin and indium. In some embodiments, the cleaning apparatus removesunwanted material deposits from the portion of the wafer handling andprocessing equipment which is near the semiconductor wafer when loadedfor processing. In some embodiments, the unwanted metal to be removedhas been deposited on the wafer handling and processing equipment inclose proximity to the edge of the semiconductor wafer, where it couldpotentially interfere with further processing of the wafer or subsequentwafers.

FIG. 1A provides a perspective view of a wafer handling and processingapparatus 100 for electrochemically treating (e.g. electroplating)semiconductor wafers, to which the disclosed cleaning methods andapparatuses may be applied. Note that although FIG. 1A illustrates aparticular wafer handling and processing apparatus, the cleaning methodsand apparatus disclosed herein may be applied to a variety of pieces ofwafer handling and processing equipment, and so the instant disclosureis not limited in application to that which is disclosed in FIG. 1A.

Wafer handling and processing apparatus 100 has various features whichare illustrated in FIG. 1A and also described with respect to subsequentFigures. Apparatus 100 includes a semiconductor wafer engaging componentwhich may be referred to as a “clamshell.” A clamshell may include a cup102 and also a cone 103 which may clamp a semiconductor wafer securelyin the cup 102.

In FIG. 1A, the cup 102 is supported by struts 104, which are connectedto a top plate 105. This assembly 102-105, collectively cup/coneassembly 101, is driven by a motor 107, via a spindle 106. Motor 107 isattached to a mounting bracket 109. The spindle 106 transmits torque toa semiconductor wafer (not shown in this figure) being held/engaged bythe cup/cone assembly 101 so that the wafer rotates during treatment(e.g. electroplating). Inside spindle 106 there may be an air cylinder(not visible in FIG. 1A) which provides a vertical force clamping thewafer between the cup 102 and cone 103. The entire assembly ofcomponents referenced as 102-109 (which includes the cup/cone assembly)is collectively referred to as wafer holder 111 in FIG. 1A. Note,however, that the concept of a “wafer holder” extends generally tovarious combinations and sub-combinations of components forengaging/holding a wafer and/or for providing mechanisms for itsmovement and positioning.

Also illustrated in FIG. 1A, is a tilting assembly 112, which mayinclude a first plate 115 slidably connected to a second plate 117. Thefirst plate 115 is also connected to a mounting bracket 109 which islocated on the distal end of the wafer holder 111. Also illustrated inFIG. 1A is a drive cylinder 113 connected to both the first plate 115and the second plate 117 at pivot joints 119 and 121, respectively.Thus, the drive cylinder 113 may provide a drive force for sliding plate115 across plate 117, thus positioning semiconductor wafer holder 111.The distal end of wafer holder 111 (the end having the mounting bracket109) thus may be moved along an arced path defined by the contact regionbetween plates 115 and 117, and therefore the proximal end of waferholder 111 having the cup/cone assembly may be tilted with respect to avirtual pivot point. In some embodiments, this allows for the angledentry of the semiconductor wafer into a treatment solution (e.g. anelectroplating bath).

The entire apparatus 100 is lifted vertically either up or down toimmerse the proximal end of wafer holder 111 into a treatment solutionvia another actuator (not shown). Thus, a two-component positioningmechanism provides both vertical movement along a trajectoryperpendicular to a treatment solution (e.g. an electrolyticelectroplating bath), and also a tilting movement allowing the positionof the wafer to deviate from a horizontal orientation relative to thesurface of the treatment solution thus providing an angled-waferimmersion capability. A more detailed description of the movementcapabilities and associated hardware of apparatus 100 is described inU.S. Pat. No. 6,551,487, filed May 31, 2001, issued Apr. 22, 2003, andtitled “METHODS AND APPARATUS FOR CONTROLLED-ANGLE WAFER IMMERSION,”which is hereby incorporated herein by reference in its entirety for allpurposes.

Note that during electroplating, apparatus 100 is typically used with aparticular plating cell having a plating chamber which houses an anodeand an electrolyte. The plating cell may also include plumbing orplumbing connections for circulating electrolyte through the platingcell, and against the wafer being electroplated. The plating cell mayalso include membranes or other separators designed to maintaindifferent electrolyte chemistries in an anode compartment versus acathode compartment.

FIG. 1B provides a more detailed view of the cup/cone assembly 101,including a cross-sectional view of cup 102 and cone 103. Note that thecup/cone assembly 101 depicted in FIG. 1B is not intended to beproportionately accurate, but rather is an exhibit stylized to promotethe clarity of the following description. Cup 102 is supported by topplate 105 via struts 104, which are attached via screws 108. Generally,a wafer 145 rests on cup 102 which is configured to support it. Cup 102also includes an opening through which a treatment solution (e.g. anelectrolyte) from the treatment cell (e.g. an electroplating cell) maycontact the wafer. Note that the wafer treatment generally takes placeon the front side 142 of wafer 145 which, for example, is where theelectroplating would occur. Thus, the periphery of wafer 145 rests onthe cup 102. Cone 103 presses down on the back side of the wafer 145 toengage it and hold it in place during a treatment process such aselectroplating. Once engaged, treatment solution may be generallysubstantially prevented from contacting the back side of the wafer 145.

To load a wafer 145 into cup/cone assembly 101, cone 103 is lifted fromits depicted position via spindle 106 until there is a sufficient gapbetween the cup 102 and the cone 103 to allow insertion of wafer 145into the cup/cone assembly 101. The wafer 145 is then inserted, in someembodiments by a robot arm, and allowed to rest lightly on the cup 102(or on a related component attached to the cup, such as a lip seal 143as described below). In some embodiments, the cone 103 is lifted fromits depicted position until it touches top plate 105. Subsequently, thecone 103 is then lowered to press and engage the wafer against theperiphery of cup 102 or attached lip seal 143 as depicted in FIG. 1B. Insome embodiments, the spindle 106 transmits both a vertical force forcausing the cone 103 to engage the wafer 145, and also the torque forrotating the cup/cone assembly 101 as well as the wafer 145 being heldby the cup/cone assembly. FIG. 1B indicates the directionality of thevertical force and rotational orientation of the torque by solid arrows150 and dashed arrows 152, respectively. In some embodiments,electroplating of the wafer 145 typically occurs while the wafer 145 isrotating. In certain such embodiments, rotating the wafer 145 duringelectroplating aids in achieving uniform plating.

In some embodiments, such as that depicted in FIG. 1B, cup 102 includesa lip seal 143, which forms a substantially fluid-tight seal against thewafer 145 when cone 103 engages wafer 145. In some embodiments, the lipseal 143 is compressible. In some embodiments, vertical force from thecone 103 presses the wafer 145 against the cup 102 and lip seal 143,compressing the lip seal 143 so as to form a substantially fluid tightseal. Thus, when engaged, the lip seal 143 generally substantiallyprevents treatment solution (e.g. an electrolytic electroplatingsolution) from reaching and contacting the backside of wafer 145 (whereit could contaminate the wafer such as by introducing contaminatingmetal atoms directly into the exposed silicon on the backside). Thissealing also generally prevents treatment solution from contacting thesensitive components of apparatus 101. In some embodiments, there mayalso be an additional seal 149 located between the cup 102 and the cone103, which engages the surfaces of the cup 102 and cone 103 to generallyform a substantially fluid-tight seal when the cone 103 engages thewafer 145. The additional sealing provided by cup/cone seal 149functions to further protect the backside of the wafer 145. Cup/coneseal 149 may be affixed to either the cup 102, or to the cone 103,engaging the alternative element when the cone 103 engages the wafer145. Cup/cone seal 149 may be a single component seal or amulti-component seal. Similarly, lip seal 143 may be a single componentseal or a multi-component seal. Furthermore, a variety of materials maybe used to construct seals 143 and 149, as would be appreciated by oneof ordinary skill in the art. For instance, in some embodiments, the lipseal is constructed of an elastomeric material, and in certain suchembodiments, a perfluoropolymer.

As outlined above, electroplating a lead-free solder alloy, such as, forexample a lead-free tin-silver alloy, tends to raise a variety oftechnical issues—some of which relate to the potential contamination andresulting required clean-up of the wafer processing apparatus used forelectroplating. Many of these issues are driven by the propensity of theelectroplating bath to: (1) sensitize the wafer supporting lip seal 143and cup 102 by exposure to stannous tin (i.e. tin having a +2 charge),and (2) cause a displacement reaction involving the tin and silver ionsin the plating bath, whereby spuriously deposited/plated tin metal isreplaced with plated silver metal. In turn, the displacement of platedtin with plated silver leads to: (1) a volume increase in spuriousdeposited metal by virtue of the differential volumes of tin and silverdeposits, and (2) increased corrosion resistance and resistance tocleaning by virtue of the higher chemical stability of the depositedsilver metal. In some circumstances, these effects can cause a rapidbuildup of spurious metal deposits on the cup 102 and on the lip seal143 of the cup, potentially leading to catastrophic failure of theapparatus's ability to perform intended functions. Spurious plating onthe cup and sealing elements alters current distribution in the waferand causes a loss of process control.

The current state of the art for handling the problem of spurious metaldeposits, and in particular, spurious deposits of tin-silver alloy, isto periodically replace various cup and lip seal holding elements (e.g.the lip seal and or cup bottom) that have accumulated spurious deposits.However, periodic replacement of the cup and/or lip seal introducessignificant cost and loss of productivity. Also, even when cleaningthese elements is possible, manual maintenance with cleaning agentsincreases the potential for cup and/or lip seal damage, excessive tooldown-time, loss of productivity, and potential exposure of tooloperators and maintenance personal to both the electroplating bath andto potentially noxious cleaning chemicals. Thus, in some embodiments,the apparatuses and methods disclosed herein may address these problemsby automating the selective cleaning and removal of unwanted metaldeposits.

Accordingly, embodiments described herein include apparatuses forcleaning and removing spurious metal deposits from one or more elementsof a semiconductor processing/treatment apparatus, and in particularremoving spurious metal deposits from a plating apparatus. In someembodiments, the one or more elements to be cleaned include the lip sealof the treatment apparatus, as well as the bottom cup region near thelip seal of the semiconductor treatment apparatus. In one embodiment,the apparatus is a swab configured to be applied to the area proximatethe cup bottom and lip seal. The swab may hold a cleaning agent thatremoves the unwanted metal deposits and selectively applies the agent tothe desired area. The swab may be configured to allow for easy wettingof the surfaces of the lip seal and cup bottom but to avoid encroachmentinto and damage of the inner sections of the cup including the wafercontact regions of the cup bottom and lip seal. In certain suchembodiments, a robotic arm may manipulate the swab and carry out thecleaning operation.

In another embodiment, the apparatus for cleaning and removing spuriousmetal deposits is a disk shaped apparatus that can fit into a waferholder assembly in place of a semiconductor wafer. Such a cleaning discmay be configured to deliver cleaning agents to the area around thecircumference of the wafer holding and positioning assembly, e.g. thelip seal and cup areas proximate the circumference of the wafer duringplating. In certain embodiments, the cleaning disc is configured toabsorb, retain, or otherwise hold a cleaning agent, and, whenappropriate, deliver the cleaning agent to the wafer cup holder andsealing area (e.g. the cup bottom and lip seal). In certain embodiments,the cleaning agent is retained by an adhesive force between the cleaningagent and one or more surfaces of the cleaning disc. In certain suchembodiments, delivery of cleaning agent to the cup bottom, lip seal,and/or to any other region of the treatment apparatus proximate to thecircumference of a wafer during plating occurs without substantiallyintroducing the cleaning agent into other parts of the treatmentapparatus—e.g., into the plating bath.

Also disclosed herein are methods for cleaning one or more elements of awafer treatment apparatus. In some embodiments, the methods may beautomated. In some embodiments, the methods employ the use of a cleaningswab. In other embodiments, the methods employ the use of a cleaningdisc. These methods may promote tool up-time, improve the quality ofcleaning operations, and also help to prevent damage to the cup bottomand lip seal which may occur as a result of manual wipe-down chemicaltreatment of the wafer contact region.

In some embodiments, selection of the cleaning agent will depend on thecomposition of the unwanted deposits to be removed. For instance,removal of unwanted tin-silver alloy deposits, may successfully employan oxidizing acid solution into which both tin and silver metal andsalts are oxidizable and/or soluble. Thus, in some embodiments, thecleaning agent may include an acid and/or oxidizing agent. A particularexample of an appropriate cleaning agent or cleaning solution forremoving tin-silver alloy deposits may thus be a solution of nitricacid. Such a solution may have, for example, a nitric acid concentrationof about or greater than 5%, 10%, 15%, 20%, 25%, 35%, or 50% by weight;or about or less than any one of these concentrations; or within a rangedefined by any pair of these concentrations. In some embodiments, acleaning agent/solution may employ multiple acids, such as, forinstance, a combination of nitric acid and hydrochloric acid (i.e. toform aqua regia) with both acids present in any of the above recitedconcentrations or within the above recited ranges of concentrations.However, other acids and combinations of acids may also beemployed—again, in any of the above recited concentrations or recitedranges of concentrations. In some embodiments, the cleaning agent may bea metal complexing agent, and typically a complexing agent selected forit's ability to complex a metal making up the deposits to be removed.For instance, a complexing agent selected as a cleaning agent may beoxalate ion since it complexes tin. In some embodiments, a silvercomplexing agent may be selected as a cleaning agent, such as variousmercapto-derivative compounds.

Cleaning Disc

In some embodiments, the apparatus for cleaning and removing spuriousmetal deposits from one or more elements of a semiconductor processingapparatus takes the form of a disk shaped apparatus dimensioned suchthat it can take the place of a semiconductor wafer loaded in theprocessing apparatus's wafer holder assembly. In certain suchembodiments, this cleaning disk is used to clean the cup bottom and lipseal areas, and is referred to as a “cup and lip-seal cleaning disc” or“CLSCD” for short. In some embodiments, the diameter of the cleaningdisc is approximately the same as that of a standard semiconductorwafer. Thus, the cleaning disc may have a diameter of about 150 mm, 200mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, or 500 mm, or the cleaningdisc's diameter may fall within a range defined by any pair of theserecited diameters. By having an approximate shape and thickness similarto that of a standard semiconductor wafer, the cleaning disc may besuitably handled and moved through a wafer treatment environment, suchas, for example, moved by a robotic wafer handler arm of a plating toolto and from various stations within the plating tool. In one embodiment,the cleaning disc may be stored within the tool, for example, in astandard wafer storage area of the tool, when the cleaning disc is notin use. In other embodiments, the cleaning disc is loaded from a platingtool as if it were a normal wafer to be processed/plated, i.e. run andprocessed from the tool loading location, and returned to the waferstorage area after processing.

One embodiment of a cleaning disc is schematically illustrated in FIG.2A, which shows a perspective view of this embodiment from below. Notethat FIG. 2A displays an exemplary embodiment, presented for explanatorypurposes—it should not be construed in any manner which limits thevarious aspects of the inventions disclosed herein. The cleaning disc200 may have a substantially circular upper surface 230, a substantiallycircular lower surface 240, a substantially circular edge 220 joiningthe upper and lower surfaces, 230 and 240, and one or more features 210allowing the cleaning disc 200 to retain a cleaning agent. In someembodiments, the cleaning disc may have a plurality of pores 210 openingat the circular edge 220 (which joins the upper and lower surfaces, 230and 240). The pores 210 may have an interior extending into the interiorof the disc 200, and be dimensions such that a cleaning agent may beretained in the interior of the pores 210 by an adhesive force betweenthe cleaning agent and the interior surface of the pores 210. Dependingon the embodiment, at the appropriate time and/or conditions thecleaning agent is released from the cleaning disc 200 so that one ormore elements of the treatment apparatus are contacted by the cleaningagent in order to remove unwanted deposits therefrom. In certain suchembodiments having a plurality of pores, cleaning agent is released fromthe interior surface of the pores.

In some embodiments, the cleaning disc 200 is a self-contained unit,configured to be pre-loaded with a cleaning agent and then inserted intothe wafer holder in order to carry out the cleaning operation. Thecleaning disc may have a cleaning agent reservoir 208 configured tosupply the dispensing features of the cleaning disc such that more thanone cleaning operation may be performed before reloading/resupplying thecleaning disc with cleaning agent. In other embodiments, the cleaningdisc is reloaded/resupplied with cleaning agent for each cleaningoperation.

The cleaning disc may be constructed of a variety of different types ofmaterials, so long as the cleaning disc is made from materialschemically and mechanically compatible with its intended use. In someembodiments, the cleaning disc is primarily made from a corrosionresistant metal such as a suitable grade of stainless steel (e.g., 304,316), or titanium, or tantalum, or appropriate alloys, for example. Incertain such embodiments, the surface of the metal may be coated with aprotective polymer film. In certain embodiments, it stands to reasonthat a sufficiently protective polymer film may facilitate the use of aless corrosion resistant metal as well. In other embodiments, thecleaning disc may be primarily made from a corrosion resistantthermoplastic polymer. A suitable variety of polymer may be a hard,stiff, generally crystalline and/or cross-linked polymer that ischemically resistant to one or more appropriate cleaning agents, such asstrongly acidic and oxidizing process chemicals, and also to thecorrosive chemicals oftentimes used in plating baths as described aboveand in more detail below. Suitable polymers include Ryton/Techron,polyphenylene sulfide (PPS), and polyvinylidene fluoride (PVDF), and insome cases Lexan™ or similar polycarbonates. Thus, in some embodiments,the cleaning disc is made from a corrosion resistant thermoplasticpolymer such as a polycarbonate, polyphenylene sulfide, polyvinylidenefluoride, or some combination of the foregoing.

FIGS. 2B and 2C illustrate a cleaning disc 200 being held in a substrateholding and processing apparatus which, in this case, is anelectroplating apparatus. Visible in both FIGS. 2B and 2C is the cupbottom 102 of the electroplating apparatus, which is typicallyelectrically isolated and, in some embodiments, constructed fromplastic. Also visible in FIGS. 2B and 2C is the lip seal 143, themetallic current-carrying contact-backing-plate ring 148, (which in someembodiments is constructed of stainless steel), the metalliccurrent-carrying buss-bar-ring 150 (also oftentimes constructed ofstainless steel, depending on the embodiment), and finally the metalliccontact member 155. In some embodiments, the metallic contact member 155is constructed of a corrosion resistant metal having a good spring forcefor making electrical contact with the semiconductor wafer. Thus, insome embodiments, the metallic contact member 155 may be constructed ofa gold or platinum coated stainless steel, or of various PalineyAg/Pd/Pt alloys such as Paliney 7. As for the spatial configuration ofthe metallic contact member 155, in some embodiments, the metalliccontact member 155 is composed of between 100 and 1000 individualreticulated contact “fingers” which are bent and joined as a continuousstrip at one end where they fit between and make a pressure contact tothe backing plate ring 148 and buss bar ring 150.

The cleaning disk 200 is placed into the cup 102 and held there in amanner similar to how a semiconductor substrate would be placed and heldin the cup 102. In some embodiments, the two sides or faces of thecleaning disc may be symmetrical, but in other embodiments, they may notbe symmetrical, and so in these embodiments, whether the cleaning discis oriented “face up” or “face down” in the cup 102 may make adifference. In some embodiments, the cleaning disc 200 may include acleaning agent delivery element 210 and possibly a cleaning agentretaining element 205. Collectively, the cleaning agent retainingelement 205 and cleaning agent delivery element 210 function to containthe cleaning agent until delivery is appropriate and then deliver it tothe elements of the processing apparatus to be cleaned. In certain suchembodiments, the elements to be cleaned are the cup bottom 102 and lipseal 143, and the cleaning disc 200 is oriented “face down” in the cup102 so that the cleaning agent retaining element 205 is oriented“downward” as shown in FIGS. 2B and 2C, and also so that the cleaningagent delivery element 210 coincides with inner periphery of the lipseal 143A and inner periphery of the cup bottom 102A. A seal between thecleaning disc 200 and the inner periphery of the lip seal 143A is madeby forcing the disc downward with a cylindrical cone (see cone 103, FIG.1B) which resides “above” the disc.

In some embodiments, cleaning agent delivery element 210 is a porousregion of the cleaning disc, composed of a suitable construction ofmaterials and structure to draw in and retain cleaning agent within itsinterior by the forces of surface tension and/or adhesion between thecleaning agent and the interior surface of the porous region. In someembodiments, the porous region may be constructed from a sponge orsponge-like material. In other embodiments, the porous region is a solidmaterial having a large number of fine holes. Thus, in some embodiments,a cleaning disc may include a plurality of pores opening at the edge ofthe cleaning disc 200 and having an interior volume extending into theinterior of the disc. In certain such embodiments, these holes or poresmay be oriented horizontally, parallel to the upper 230 and lower 240surfaces of cleaning disc 200, although in other embodiments, theholes/pores may not be quite horizontal, or may have kinks and/or turnsmaking portions of the pores not parallel with the top and bottomsurfaces. Although various pore/hole configurations are possible, theholes/pores are typically dimensioned such that a cleaning agent may beretained in the interior of the pores by an adhesive force between thecleaning agent and the interior surface of the pores. Thus, in someembodiments, the interior surfaces of the holes/pores and cleaning agentdelivery element 210 (and possibly cleaning agent retaining element 205)are hydrophilic in order to enhance the cleaning agent fluid retentionproperties of these elements via surface tension interactions andadhesive forces.

In some embodiments, the pores making up the cleaning agent deliveryelement 210 may be formed by drilling holes into a suitable metallic orthermoplastic material. For example, the holes can be drilled into acorrosion resistant metal such as titanium, or into a hydrophilicthermoplastic such as Ryton. In some embodiments, the holes may have adiameter about or between 0.25 mm and 1.25 mm, or more particularly,about or between 0.5 mm and 1.0 mm, or yet more particularly, about orbetween 0.7 mm and 0.8 mm. In some embodiments, regions of the cleaningdisc 200 other than the cleaning agent delivery element 210 (andpossibly the cleaning agent retaining element 205), such as otherportions of the disc edge as well as the top and bottom surfaces of thedisc may preferably (but not necessarily) be hydrophobic in order tominimize cleaning agent fluid retention in these other regions. Forexample, a cleaning disc 200 made of titanium or a PPS/Ryton/Techtrontype plastic and having drilled holes as the cleaning agent deliveryelement 210 may be coated with a hydrophobic film everywhere else on thedisc, such as at the periphery and/or other interior sections of thedisc.

Referring again to FIGS. 2A through 2C, in some embodiments, thecleaning agent delivery element 210 and any associated pores/holes 210may be located in a substantially circular edge 220 joining the upper230 and lower 240 surfaces of the disc 200. In some embodiments, thisedge 220 has a step built into it so that while a upper portion 222 ofthe edge 220 is configured to rest on the lip seal 143 of the cup bottom102, a lower portion 224 of the edge 220 is configured to be adjacent tothe inner periphery of the lip seal 143A and cup bottom 102A once thedisc 200 is loaded into the holding and processing apparatus. Thus, ifthe lower portion 224 is configured to deliver cleaning agent viacleaning agent delivery element 210, then when the cleaning disc 200 isloaded “face down” into the holding and processing apparatus, thecleaning agent delivery element 210 will be oriented adjacent to theinner peripheries of the lip seal 143A and cup bottom 102A, as shown inFIGS. 2B and 2C. In configurations having a plurality of pores/holesconfigured to retain cleaning agent, the pores/holes may have theiropenings located in the lower portion 224 of edge 220. Thus, the lowerportion 224 of edge 220 may have a radius less than that of the upperportion 222. In some embodiments, the lower portion 224 of edge 220 mayhave a height which is substantially the same height as or somewhatlarger than the combined height of the inner peripheries of the lip seal143A and cup bottom 102A. Thus, in certain such embodiments, forexample, the lower portion 224 may be about 2 mm tall. More generally,depending on the embodiment, the mean height of the portion of the edge220 having pores may be about or between 0.5 mm and 3.5 mm, or moreparticularly, about or between 1.0 mm and 3.0 mm, or still moreparticularly, about or between 1.5 mm and 2.5 mm. As indicated above, insome embodiments, the height of the portion of the edge 220 havingpores/holes is selected to substantially coincide with the combinedheight of the inner periphery of the lip seal 143A and the innerperiphery of the cup bottom 102A. In some embodiments, the lower portion224 is located slightly inwards from the inner periphery of the cupbottom 102A and the inner periphery of the lip seal 143A. In certainsuch embodiments, the lower portion 224 of edge 220 may be located about1 mm inwards from the 143A and 102A surfaces. Furthermore, so that theupper portion 222 of edge 220 may rest on the cup 102 and lip seal 143while the lower portion 224 is adjacent to but not physically contactingthe inner periphery of the cup 102A and lip seal 143A, the lower portion224 is located slightly inwards from the upper portion 222—i.e. theradius of the upper portion 222 of edge 220 is slightly larger than theradius of the lower portion 224.

In some embodiments, such as the cleaning disc schematically illustratedin FIG. 2A, there are a large number of individual cleaning agentdelivery elements/holes 210 around the circumference of the disc, andthere is also an inward chamber 208 slotted radially inwards from theholes 210 (i.e. inward chamber 208 is a continuous slot around thecircumference of the disc). Optionally, within the inward chamber 208 isplaced an adsorbent element, such as, for example, a wicking fibrousmaterial, or a fabric or cloth, or a filter material, or other suitablematerial that can wick and retain cleaning agent within the inwardchamber 208 of the cleaning disc 200. In principle, as would beunderstood by one having ordinary skill in the art, any suitablematerial may be used to form the cleaning agent adsorbent element withininward chamber 208, so long as it is capable of retaining a typicallysufficient and/or useful amount of cleaning agent. In certainembodiments, the inward chamber 208 may take the form of an cut out“cavity” annular shaped inward volume, typically between about 0.5 cmand 3 cm in width (viewed radially inwards from the lip seal interface).In one embodiment, the inward chamber 208 is about or between 1 cm and 2cm in width. In some embodiments, the inward chamber 208 may be anannular shaped region which opens on the bottom surface of the disc. Inother embodiments (not shown in FIG. 2A), a portion of inward chamber208 may be covered by a portion of cleaning agent retaining element205—i.e. so that a portion of the inward chamber 208 is underneath someportion of the bottom surface of the disc. In certain such embodiments,the inward chamber 208 may be entirely covered by cleaning agentretaining element 205—i.e. so that substantially all (other than perhapsa cleaning agent loading port) is underneath some portion of the bottomsurface of the disc. Note, however, that in other embodiments, thecleaning disc 200 may have no inward chamber, and the cleaning agent mayjust be retained in the large number of azimuthally arranged holes whichstore the cleaning agent until it is released for cleaning.

In the specific embodiment cleaning disc 200 schematically illustratedin FIG. 2C, the bottom portion 224 of edge 220 is approximately 1.6 mm,and consists of a large number (about 600-700) of roughly equal sizedholes having a diameter of approximately 0.76 mm. The holes have beendrilled into the bottom portion 224 of edge 220 inwards in the radialdirection. Each small hole/pore represents a cleaning agent deliveryelement 210 functioning to hold and retain cleaning agent by itsadhesive force with the cleaning agent and by the cleaning agent'sforces of surface tension.

Note that the specific embodiment cleaning disc 200 shown in FIG. 2C isan exemplary embodiment and is presented for explanatory purposes—itshould not be construed in any manner which limits the various aspectsof the inventions disclosed herein. Cleaning disc 200 presented in FIG.2C is dimensioned for an inner lip seal having a diameter of about 2.25mm (which means, for example, that a 300 mm wafer would have an exposedarea of diameter 295.5 mm (300 mm-2×2.25 mm). Generally, if holes areused for the cleaning agent delivery elements 210, it is oftentimesuseful for the holes 210 to have a diameter of about 3/64 inch (1.2 mm)or less. The choice often depends on the viscosity of the cleaningagent, the amount of cleaning agent needed, and similar factors. In somecases, if the holes are significantly larger, they will not retain thefluid as well, and they may also be unnecessarily larger than thecombined height of the lip seal and cup bottom intended to be cleaned.On the other hand, if the holes are very much smaller, e.g. havingdiameters of less than about 0.25 mm, they will tend to retain the fluidmore strongly making it more difficult to extract the fluid and contactit with the intended treatment area as describe in more detail below.Smaller holes may also be more difficult to create by drilling.Depending on the embodiment, holes may be drilled through the bottomportion of the edge in a straight radially outwards fashion, or drilledwith some angle relative to the disc center. In some embodiments,different holes may be drilled with different angles relative to thedisc center.

As mentioned above, in some embodiments, the cleaning disc may define anannular inward chamber 208 filled with an adsorbent element which mayinclude a porous structure. The porous structure may include a sinteredmaterial, some sponge-like material, or any other porous material whichis relatively corrosion resistant and possess pores sized appropriatelyto hold and retain an appropriate cleaning agent. However, the cleaningagent should optimally not be so strongly retained by the porousmaterial that it cannot be directed to exit the pores withoutunreasonably high centrifugal forces and/or without requiringexcessively high rotation rates in order to free the fluid from thepores (e.g., greater than about 1500 RPM) when appropriate in order tocontact the elements to be cleaned. As described in more detail below,in some embodiments, cleaning agent is directed toward the periphery ofthe cleaning disc 200 by the centrifugal force created upon the spinningof the cleaning disc 200 by the substrate holding and processingapparatus, similarly to how a semiconductor wafer would be spun duringan electroplating procedure.

The central inner section of the disc, on the upper surface and/or thelower surface of the cleaning disc 200 can have ribs and/or crossmembers emanating from the center of the disc to the peripheral cleaningagent retaining areas, in order to improve mechanical rigidity and/orcontrol the flow of the cleaning agent across the disc and into thecleaning agent retaining areas (for example, in embodiments where thepores 210 are filled by application of the cleaning agent to the centerof the disc followed by rotation, the ribs or cross members are on thesame surface as pores 210 and direct fluid into those pores.

Thus, a cleaning disc can be preloaded with a cleaning agent, loadedinto a substrate holding and processing apparatus, and then spun inorder to dispense the cleaning agent selectively to the periphery of thecleaning disc, thereby cleaning the elements of the processing apparatusproximate to the cleaning disc's periphery. Various embodiment methodsof cleaning elements of a substrate holding and processing apparatus,and in particular an electroplating apparatus, are described in moredetail below which utilize the cleaning discs disclosed herein. Alsodisclosed are methods employing robotic wafer handlers and the like.Plating tools employing such methods are sold under the trade name“Sabre™ 3D tools,” available from Novellus Systems, of San Jose, Calif.

Methods of Cleaning a Semiconductor Processing Apparatus Using aCleaning Disc Including an Automated Tool Approach

Also disclosed herein are methods of cleaning one or more elements of asemiconductor holding and processing apparatus. In some embodiments, theone or more elements to be cleaned include the cup bottom and lip sealof the processing apparatus, and in some embodiments, the cleaningmethods utilize a cleaning disc as described above. Some of the cleaningmethods disclosed herein are described in reference to, and may beemployed in the context of, an automated tool-integrated approach.However, it should be understood that those skilled in the art wouldappreciate that other approaches, including approaches involving manualoperations, can also be performed or substituted to accomplish some orall of the operations described below. Accordingly, although embodimentmethods are described in the context of an automated integrated toolapproach and, in particular, the automated wafer plating tool apparatus300 illustrated in FIG. 3, a more general approach is also beingdisclosed as schematically illustrated by the flowchart of FIG. 4.

Reference is now made to FIG. 3, which is a schematic drawing of onesuitable automated wafer plating tool apparatus 300 configured to platea semiconductor wafer (e.g. silicon) or similar substrate (glass coatedthinned wafer, GaAs, ceramic, etc.) with various metals and alloys (e.g.copper, nickel, gold, palladium, cobalt, indium, tin, lead, lead-tin,tin-silver, FeCo), and perform other necessary plating sub-processes(e.g. spin rinsing and drying, metal and silicon wet etching,electroless deposition, pre-wetting and pre-chemical treating,photoresist stripping, surface pre-activation). The automated waferplating tool apparatus is shown schematically looking top down in FIG.3, and only a single level or “floor” is revealed in the Figure, but itis readily understood by one of ordinary skill in the art that such anapparatus, e.g. the Novellus Sabre™ 3D tool, can have two or more levels“stacked” on top of each other, each potentially having identical ordifferent types of processing stations.

As mentioned above, in some embodiments, contamination in the scenarioof tin-silver solder alloy plating is of particular interest because itis known these scenarios generally have the problem of creating spuriousmetal deposits on and around the wafer holding cup and lip seal overtime. Accordingly, oftentimes with repeated use periodic maintenance isrequired to remove and clean the metallic deposits and other filmbuildup. Furthermore, since spuriously plated metal deposits on thesealing area and its vicinity divert current and otherwise change theintended pattern of current distribution, removal of these deposits isdesired to maintain good within wafer uniformity and particleperformance.

Referring again to FIG. 3, the wafers 306 that are to be processed aregenerally feed to the automated plating tool 300 through a front endloading “foup” 301 and, in this example, are brought from the foup tothe main wafer processing area of the tool via a front-end robot 302that can retract and move a wafer in multiple dimensions from onestation to another of the accessible stations—two front-end accessiblecleaning agent loading stations 304 and also two front-end accessiblespin rinse drying (SRD) stations 308 are shown in this example. Alsoshown in the example are two tin-silver alloy plating cells 307. Lateralmovement from side to side of the front-end robot 302 is accomplishedutilizing robot track 302A.

In some embodiments, a cleaning method 400, as schematically illustratedin FIG. 4, is initiated as follows. A data processing system within orconnected to the automated plating tool 300 tracks the plating of wafers306 by the tin-silver alloy plating cell 307, and when the dataprocessing system determines that cleaning the plating cell 307 isnecessary and/or desirable (e.g. typically after 50 to 200 wafers ormore have been plated, depending on the deposition rate and chargepassed per wafer), the system initiates an automated cleaning process.First, the system designates as temporarily unavailable the stations tobe cleaned—e.g. the two plating cells 307. Once so designated, furtherplating in plating cells 307 is postponed until the cleaning operationis completed. Note that in a manual cleaning process, the plating cells307 would need to be denoted by an operator as having completed themanual cleaning operation before plating could be resumed, but in theautomated process, the data processing system initiates cleaning and,when complete, designates plating cells 307 available for plating onceagain, and thereafter until the predesignated cleaning interval arisesor some other criteria is again met.

Once initiated, in some embodiments, a cleaning method 400 proceeds asfollows. First, again referring to FIG. 3, the automated wafer platingtool apparatus 300 uses front-end robot 302 to extract a cleaning disc200 from the cleaning disc storage area 303 and place the cleaning discin one of the two cleaning agent loading stations 304. (Note that intools such as the Novellus Sabre™ 3D plating tool where operations arerun in cell pairs—or Duets—the two cell modules of each Duet operate atthe same time, so a step in the cleaning sequence will not begin untilboth Duets are ready.)

Next, cleaning agent is loaded into the cleaning disc 200 (see step 410of FIG. 4). In some embodiments, the cleaning agent may be stored at acleaning agent loading station 304 within the automated wafer platingtool apparatus 300, which may reside, for example, on the plating tool'sleft front and upper deck. Within the cleaning agent loading station304, a suitable volume of cleaning agent may be stored in a dosing sizelike bottle. In one embodiment, the cleaning disc is placed “face up” ina cleaning agent loading station 304 which contains a disc supportingchuck that can apply cleaning agent to the cleaning disc 200 by, forexample, generally delivering a stream or spray to the disc face andhaving the cleaning agent flow radially outwards due to viscous forcesfrom simultaneously rotating the disc. The disc is held “face up” whilecleaning agent is applied and the disc is held in a wafer holding chuckand spun at about or between 50 and 300 RPM. In some embodiments, thismethod of application is designed so as to avoid getting cleaning agentonto the backside of the cleaning disc and potentially subsequentlycontaminating the tool's robotic wafer/disc handling arm or otherelements. Note that the “face” of the cleaning disc is the side of thedisc having the cleaning fluid delivery elements (e.g. the surface withthe protrusion having cleaning agent retaining element 205, see FIG. 2A)and what is referred to as the lower surface or back of the cleaningdisc is the other side, which in some embodiments, comprises asubstantially flat surface. “Face up” therefore refers to the discorientation of the “face” away from the center of the earth, and “facedown” refers to the “face” oriented towards the center of the earth.Thus, while supplying fluid and spinning the cleaning disc face up inthe cleaning agent loading station, the process fills the disc cleaningperiphery fluid retention region as the spray or stream of the cleaningagent is applied to the general center of the disc face of the cleaningdisc, builds up and move outwards. As the disk spins the cleaning agentis retained on the general face of the disc by gravity and move radiallyoutwards as it is spun, filling the cleaning agent storage and deliveryelements 210, e.g. the holes/pores, with cleaning chemical Excesscleaning agent passes over the cleaning agent delivery elements 210while the elements 210 (e.g. the drilled holes/pores) fill and retainthe cleaning agent. The rotational speed and size of the holes/pores maybe optimized to allow retention of cleaning agent within the holes/poreswhile allowing the excess cleaning agent to flow off the disc. Once thecleaning agent delivery elements 210 are filled, the flow may be stoppedand the appropriate rotation speed is applied, removing excess fluid, sothat the disc is essentially free of cleaning agent except in thecleaning agent delivery elements 210 of the disc (e.g. the drilledholes/pores). In other embodiments, cleaning agent is loaded into thecleaning disc 200 (step 410 of FIG. 4) by immersing the cleaning disc200 into a tank containing the cleaning agent. Depending on theembodiment, the cleaning disc may only be partially immersed, but in anyevent, it is immersed to an extent sufficient to allow cleaning agent tobe drawn into the cleaning agent delivery elements 210 of the cleaningdisc 200—for instance, by capillary action. Of course, the cleaningagent delivery element 210 may take the form of drilled holes or pores,or it may be composed of a porous sintered material as described abovein reference to FIGS. 2A through 2C. In either of these exemplaryembodiment methods, the cleaning agent is loaded into the cleaning disc(step 410) by receiving the cleaning agent into the cleaning agentdelivery elements 210 of the cleaning disc where it is held (step 420)until needed. In some embodiments, the cleaning agent is held (step 420)in the cleaning disc by adhesion to the interior surfaces of theplurality of pores.

In some embodiment methods, the loading of the cleaning agent into thecleaning disc (step 420) is followed by a step of removing cleaningagent from one or more outside surfaces of the disc (step 430),typically prior to the next step in the cleaning method (e.g. thepositioning step 440). In some embodiments, such as described above,cleaning agent is removed simply by stopping the flow of cleaning agentduring the loading step 420 and allowing the cleaning disc to continuerotating so that the remaining cleaning agent flows off the surface ofthe disc. In certain embodiments, the rate of rotation may be increasedto promote shedding of the cleaning agent once the flow of cleaningagent has been stopped, however, the rotation rate would not typicallybe increased to the point where cleaning agent flows out of thepores/holes. Even if application of cleaning agent is not accompanied byspinning the cleaning disc, during the step of removing cleaning agent(step 430), spinning may still be employed to promote removal ofcleaning agent, and, similarly, a selected rotation rate would typicallybe sufficiently fast to cause any cleaning agent remaining on theoutside surfaces to flow off the disc, but sufficiently slow such thatcleaning agent within the disc's plurality of pores substantiallyremains within the plurality of pores. In certain such embodiments, thisrotation rate is about or between 50 RPM and 250 RPM for a period of 5to 60 seconds.

In some embodiments, the removal of cleaning agent from the outsidesurface (step 430) may include rinsing one or more outside surfaces witha rinsing agent. In certain such embodiments, the rinsing is accompaniedby spinning as described above, and in certain embodiments spinning maynot be necessary. If the disc is spun, selection of a rinsing agent witha viscosity less than the cleaning agent may help promote the selectionof a suitable spin rate. In some embodiments, water or distilled anddeionized water may serve as a suitable rinsing agent. Thus, in someembodiments, water may be applied to the outside surfaces of thecleaning disc for a short time while the cleaning disc is rotated at asuitably slow speed so as to aid in the flushing of the outside surfacesof excess cleaning agent, and thereafter, excess cleaning fluidentrained on the outside surfaces of the disk may be removed by spinningthe disc at an appropriate higher speed so that fluid remains in theplurality of pores but flows off of the main outside surfaces.Alternatively or in addition to these steps, forced air drying may beemployed to remove any excess cleaning agent or rinsing agent. As aresult of one of the above embodiment removal steps (step 430), thepores/holes of the cleaning disc are filled with cleaning agent, but thesurfaces of the cleaning disc are substantial free of the same. At thispoint, cleaning agent will then be held in the cleaning disc (step 440)until it is appropriate for it to be released for contacting the one ormore elements of the apparatus to be cleaned.

Once cleaning agent has been loaded (step 410) and held (step 420) inthe cleaning agent delivery elements 210 of the cleaning disc 200, andany removal or rinsing has been performed (step 430), the cleaning discis positioned in the processing apparatus (step 440) so that it may beused to clean various elements of the processing apparatus. In someembodiments, the cleaning disc 200 is transported by the back end robot309 to tin-silver alloy plating station 307, and inserted into theclamshell of plating station 307 similar to as illustrated above inFIGS. 2A and 2B. In some embodiments, the cleaning disc 200 isspecifically positioned within the processing apparatus (step 440) suchthat a plurality of pores/holes in the cleaning disc holding cleaningagent are adjacent to the one or more elements to be cleaned (whichwould normally be adjacent to a semiconductor wafer, when a wafer isheld in the clamshell assembly). As with the front end robot 302, theback end robot 309 is also shown positioned on a track and is capable oftransporting either semiconductor wafer or cleaning disc 200 from theforward cleaning agent loading station 304 to any of the upper or lowerdecks of the processing tool 300, and to any processing stationthroughout the processing tool 300. Once the back end robot 309 placesthe cleaning agent holding cleaning disc 200 into the cup (see 102,FIGS. 1B, 2A, and 2B), the cone (103, FIG. 1B) is lowered, closing thewafer holding clamshell (cup and cone), and forming a seal between theedge of the cleaning disc 200 and the lip seal 143 (FIGS. 1B, 2A, and2B).

Once the cleaning disc 200 is positioned within the processingapparatus, a step 450 of releasing cleaning agent from the disc'scleaning agent delivery elements is performed. In some embodiments, thecleaning agent is released from a plurality of pores such that the oneor more elements of the apparatus to be cleaned are contacted by thereleased cleaning agent. In some embodiments, this is accomplished byspinning the clamshell and cleaning disc at an appropriate rotationalrate to force out cleaning agent from the plurality of pores/holes (by,e.g., centrifugal forces overcoming forces of surface tension and/oradhesion) so as to contact and wet the inner periphery of the lip seal143A and the cup bottom 102A, but not to allow, for example, thesubstantially continuous flow of cleaning agent out of the plurality ofpores/holes and off of the disc and cup bottom. Suitable rotation ratesrange from about 50 to about 500 RPM depending on the hole sizes, thesurface tension of the cleaning agent, the strength of the adhesionbetween the cleaning agent and the various surfaces of the cup bottomand lip seal, the viscosity of the cleaning agent, and the size of thegap separating the pores/holes from the inner peripheries of the lipseal 143A and cup bottom 102A. Rotation of the cleaning disc iscontinued so that the inner periphery of the lip seal and cup bottom areexposed and contacted with the cleaning chemical generally anywhere from10 seconds to 3 minutes, largely depending on the strength of thecleaning agent and the amount of spurious metal deposit and buildup.Accordingly, in some embodiments, the one or more elements of theprocessing apparatus to be cleaned may be contacted with cleaning agentfor about 1 second, 5 seconds, 10 seconds, 20 seconds, 30 seconds, 1minute, 2 minutes, 2.5 minutes, 3 minutes, or 3.5 minutes, or, in someembodiments, a range of contact times may be appropriate, such as anyrange defined by any pair of the aforementioned contact times. Thus, forexample, an appropriate range of contact times may be from 1 second to3.5 minutes, or from 5 seconds to 30 seconds, or from 30 seconds to 3minutes.

Thereafter, in some embodiments, before the cleaning disc is removedfrom the clamshell, the cleaning disc is spun at a sufficiently highrate (e.g., greater than 500 RPM) to remove the cleaning agent from thegap separating the cleaning agent delivery elements 210 from the lipseal and cup bottom. In some embodiments, spent cleaning agent will thenflow radially outward along the bottom of the cup surface and into awaste collection area of the plating cell. This is followed optionallyby a distilled deionized water rinsing step with the cleaning diskspinning at sufficiently high speed so as to flush the pores of the discand the aforementioned gap of cleaning agent with water.

In other embodiments, before the cleaning disc is removed from theclamshell, reduction in the rotation rate causes some or a majority ofthe cleaning agent to be sucked back into the pores/holes (step 460).Afterwards, the cleaning disc may be removed from the clamshell andprocessing apparatus (step 470). Optionally, after removal of thecleaning disc, a flat or blanket “dummy” non-functioning-device wafer isdrawn from the dummy wafer storage area 303 and placed into theclamshell after the above cleaning operation, and the lip seal assemblyis rinsed with distilled deionized water with the blanket dummy wafer inthe clamshell, so as to remove residual cleaning agent from the lipseal. This can be followed optionally by a cup and cone rinsing (CCR)operation so as to clean the lip seal, cup internals such as electricalcontacts, and the cone interfaces.

In some embodiments, after removal from the clamshell of the processingapparatus which was cleaned, the cleaning disc 200 is moved (e.g., byback end robot 309) to a spin rinse drying (SRD) station 308, where anyremaining cleaning agent may be unloaded from the cleaning agentdelivery elements 210 (step 480). In some embodiments, the cleaning discmay be first optionally spun (e.g. face up or face down while held in awafer holding chuck at a high speed, e.g. 500-2000 RPM) to remove mostof the entrained cleaning agent held in the pores/holes of the disc. Insome embodiments, this spin operation is then followed by one or morewater dispensing and pore/hole flushing/absorption/rinsing steps anddrying/spinning steps so as to flush any remaining cleaning agent out ofthe disc pores and also from the disc surface.

In some embodiments, the disc undergoes a high speed (e.g. 1000 to 2000RPM) drying step to remove all fluids from the disc surfaces and fluidretaining pores/holes/elements. After this, the cleaning disc isextracted by the front end robot 302 and returned dry to the dummy waferstorage area 303 for reuse at a later time.

Finally, note that the foregoing disclosed cleaning apparatuses andcleaning methods may be employed as part of an autocleaning procedureused in a method of processing a series of semiconductor substrates.Methods of electroplating a sequence of substrates employing anautocleaning procedure are described in U.S. Provisional PatentApplication No. 61/676,841, filed Jul. 27, 2012, titled “METHODS ANDSYSTEMS FOR CLEANING ELECTROPLATING SUBSTRATE HOLDERS,” which is herebyincorporated by reference in its entirety herein for all purposes. Thus,for instance, a method of electroplating a sequence of semiconductorwafers employing an autocleaning step, may utilized the cleaning discsand cleaning methods disclosed herein during the autocleaning step.Various factors potentially considered when deciding whether initiationof a sequence of automated cleaning steps is warranted are described indetail in the foregoing provisional US patent application, such as, forexample, whether a predetermined number of wafers have been plated sincethe last cleaning.

Other Embodiments

Although the foregoing embodiments have been described in some detailfor purposes of clarity and understanding, it will be apparent to one ofordinary skill in the art that certain changes and modifications may bepracticed. Therefore, the disclosed embodiments are to be viewed asillustrative rather than restrictive, and the breadth of this disclosureis not to be limited in scope to the specific details provided hereinbut rather may be modified within the appropriate scope and equivalentsas would be understood by one of ordinary skill in the art.

We claim:
 1. A method of cleaning one or more elements of asemiconductor holding and processing apparatus, the method comprising:loading a cleaning agent into a cleaning disc by receiving the cleaningagent into a plurality of pores opening in one or more edges of the discand extending into the interior of the disc; holding the cleaning agentinside the plurality of pores; positioning the cleaning disc within theprocessing apparatus such that the plurality of pores are adjacent tothe one or more elements of the apparatus to be cleaned, the one or moreelements to be cleaned normally being adjacent to a semiconductor waferwhen a wafer is held in the processing apparatus for processing; andreleasing cleaning agent from the plurality of pores such that the oneor more elements of the apparatus to be cleaned are contacted by thereleased cleaning agent.
 2. The method of claim 1, wherein the method ofcleaning is used to clean a semiconductor holding and processingapparatus after the apparatus has been used to electroplate asemiconductor wafer.
 3. The method of claim 1, further comprising:removing cleaning agent from one or more outside surfaces of the disc,after the loading step but prior to the positioning step; wherein theremoving of cleaning agent comprises spinning the disc at a rotationrate such that cleaning agent flows off one or more outside surfaces ofthe disc, but cleaning agent substantially remains within the pluralityof pores.
 4. The method of claim 3, wherein the rotation rate is aboutor between 50 RPM and 250 RPM.
 5. The method of claim 1, furthercomprising: removing cleaning agent from one or more outside surfaces ofthe disc, after the loading step but prior to the positioning step;wherein the removing of cleaning agent comprises rinsing one or moreoutside surfaces of the disc with a rinsing agent and spinning the discat a rotation rate such that rinsing agent flows off of the one or moreoutside surfaces of the disc, but cleaning agent substantially remainswithin the plurality of pores.
 6. The method of claim 5, wherein theviscosity of the rinsing agent is less than the viscosity of thecleaning agent.
 7. The method of claim 1, wherein the loading of thecleaning agent further comprises: immersing a portion of the disc in thecleaning agent; and drawing the cleaning agent into the pores bycapillary action.
 8. The method of claim 1, wherein the holding of thecleaning agent further comprises: adhering the cleaning agent to theinterior surfaces of the plurality of pores.
 9. The method of claim 1,wherein the releasing of cleaning agent from the plurality of porescomprises spinning the disc at a rotation rate such that the one or moreelements to be cleaned are contacted by the released cleaning agent, butthe released cleaning agent does not substantially flow continuously outof the plurality of pores.
 10. The method of claim 9, further comprisingsucking cleaning agent back into the plurality of pores, after beingreleased to contact the one or more elements to be cleaned in thereleasing step, wherein the suction is created by reducing the rotationrate of the disc relative to the releasing step.
 11. The method of claim10, further comprising: removing the disc from the processing apparatus;and unloading cleaning agent from the plurality of pores by spinning thedisc at a rotation rate of about or greater than 500 rpm.
 12. The methodof claim 1, wherein the one or more elements to be cleaned comprise thelip seal of the processing apparatus and the cup bottom of theprocessing apparatus.
 13. The method of claim 12, wherein the releasedcleaning agent removes metal deposits from the one or more elements tobe cleaned.
 14. The method of claim 13, wherein the metal depositscomprise an alloy of tin and/or an alloy of indium.
 15. The method ofclaim 1, wherein the cleaning agent comprises an acid.
 16. The method ofclaim 15, wherein the acid is nitric acid having a concentration in thecleaning agent of about 10% or more by weight.
 17. The method of claim1, wherein the cleaning agent is a metal complexing agent.
 18. Themethod of claim 1, wherein the plurality of pores have substantiallycircular openings with diameters about or between 0.25 mm and 1.25 mm.19. The method of claim 1, wherein the plurality of pores extend intothe interior of the cleaning disc in between a substantially non-porousportion of an upper surface of the disc and a substantially non-porousportion of a lower surface of the disc.
 20. The method of claim 19,wherein the plurality of pores have substantially circular openings withdiameters about or between 0.25 mm and 1.25 mm.
 21. The method of claim1, wherein at least one of the edges of the cleaning disc in which theplurality of pores open comprises: a substantially circular upperportion joined to an upper surface of the disc; and a substantiallycircular lower portion joined to a lower surface of the disc, the lowerportion having a radius less than the radius of the upper portion;wherein the openings of the plurality of pores open in the lower portionof the edge.
 22. The method of claim 21, wherein the disc furthercomprises a cleaning agent adsorbent element located within a chamberradially inward from the plurality of pores, the adsorbent elementconfigured to supply cleaning agent to the plurality of pores.